In general, upon manufacturing an integrated circuit (IC) or a logic circuit, a process for forming a desired thin film on a surface of an object to be treated such as a semiconductor wafer or a LCD substrate, or a process for etching the thin film in a desired pattern, etc., are repeatedly performed.
Taking a film forming process as an example, it is possible to form a thin film of a silicon, a thin film of a silicon oxide or nitride, a metallic thin film, or a thin film of a metal oxide or nitride on the surface of the object to be treated, by reacting predetermined process gases (source gas) within a treatment container.
Herein, when the film forming process is performed, an extra reaction by-product is generated and discharged with an exhaust gas. Also, an unreacted process gas is discharged.
The reaction by-products or unreacted process gases become a cause of an environmental pollution when discharged directly to the atmosphere. Accordingly, in general, a trapping mechanism which is provided in an exhaust system extending from the process vessel has trapped and removed, for example, the reaction by-product or unreacted process gas contained in the exhaust gas.
Various configurations of the trapping mechanism have been proposed depending upon the properties of the reaction by-product to be trapped and removed. For example, the trapping mechanism for removing a reaction by-product which is condensed (liquefied) or coagulated (solidified) in a room temperature, is constituted by installing a plurality of fins in a case having an exhaust gas inlet and outlet. The fins are sequentially arranged in a flow direction of the exhaust gas, and the reaction by-product is caused to be trapped in such a manner that the reaction by-product in the exhaust gas is attached to the surface of the fins when the exhaust gas flows between the fins. Further, by cooling the fins with a cooling medium etc., it is possible to improve the trapping efficiency (see, for example, Japanese Patent Laid-open Publication No. 2001-214272).
Recently, in order to decrease resistances such as a wiring resistance, or a contact resistance, a raw material (source gas) of an organic metallic compound containing a metal such as silver, gold and ruthenium has been used to form a thin film by a film forming apparatus. In this case, a method has been proposed for recovering the by-product containing unreacted raw material, by cooling and condensing the exhaust gas and also refining the by-product to obtain the unreacted raw material (see, for example, Japanese Patent Laid-open Publication No. 2001-342566).
However, when the above mentioned organic metallic compound is used, there may be a reaction type in which the organic metallic compound is not dissolved in water well and a product other than a reaction by-product generated by the decomposition of the raw material itself is not generated, as in a carbonyl based organic metallic compound. In this case, when the recovery method including a refining process mentioned in Japanese Patent Laid-open Publication No. 2001-342566 is used, an overall process becomes too complex.